Radio frequency identification (RFID), also known as electronic tag, is a wireless communication technology that can be identified or perform data exchange with a read and write device through radio waves. An electronic tag mainly includes an antenna and an identification chip. In order to reduce the size and cost, many electronic tags use passive power design, which means that the power source of the identification chip is generated by microwave resonance or electromagnetic induction by using the antenna or coil to sense the radio waves or magnetic fields sent from the read and write devices.
Many industries use electronic tags. For example, electronic tags may be attached to a car in production, and therefore, the progress of the car in the production line can be tracked; through electronic tags, warehouse can track the location of items and logistics management can be facilitated; electronic tags may be set on the identification card for access control management, installed in the car for collecting road toll and parking fees, installed in livestock or wildlife for identification, or linked to electronic records of patients. The use of electronic tags is very broad.
For longer distance communications, an antenna is used for general wireless transmission. Specifically, radio waves produce microwave resonance first. The antenna, after receiving the radio waves from a read and write device, then transmits the radio waves to the modulation circuit and power control circuit in the identification chip. The power control circuit converts the transmitted AC into DC as the power sources of the components in the identification chip. After obtaining the power source, logic unit starts to process the received data. Once the processing is completed, the logic unit modulates the result by the modulation circuit, and then transmits back to the remote read and write device through the antenna. Thus, the power supply and data exchange functions are completed.
Design of the antenna of an electronic tag requires that the antenna has a frequency band matching with the radio waves, to generate sufficient power by induction, and to consider the gain effect and read field shape. Further, to consider the antenna impedance matching, increase the communication distance, optimize the read rate of data, and consider the application of miniaturization, the type of the antenna must be designed specific to such purposes.
Accordingly, one objective of the present invention to provide a slot antenna structure for use in an electronic tag, which achieves the above-mentioned objectives and solves the problems in the prior art.